Methods for treatment and disposal of regulated medical waste

ABSTRACT

A method for safely treating and disposing of infectious biomedical waste and other hazardous materials is disclosed. The method involves alkaline hydrolysis of infectious agents contained in regulated medical waste or hazardous waste solutions. The infectious waste is immersed into a highly basic solvent (&gt;130° C., &gt;2.79 atm) until the hydrolyzable matter is fully digested, thereby forming a sterile solution and sterile solid waste. The sterile solution and solid waste may then be disposed of through standard means, such as in a sanitary sewage system or local landfill facility. The method also provides for the treatment of lipid soluble hazardous material contained in the regulated medical waste.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application is a continuation in part application ofearlier copending U.S. patent application Ser. No. 09/171,447, filedOct. 20, 1998.

TECHNICAL FIELD

[0002] The present invention relates to the field of waste disposal.More particularly, the invention relates to methods for safely treatingand disposing of infectious biomedical waste and other hazardousmaterials.

BACKGROUND OF THE INVENTION

[0003] Today hospitals and other health-care organizations produceconsiderable amounts of infectious waste. This type of waste includessurgical gowns, surgical gloves, needles, instruments, glass, culturedishes, and other disposable matter exposed to blood and other bodyfluids of patients. Such waste is classified as “regulated medicalwaste” under federal regulations, disposal of which must comply withstrict governmental regulations. As used herein, the term “regulatedmedical waste” refers to infectious waste, to waste containinginfectious agents, as defined below, and to any waste that poses athreat of transmission of infection to humans or animals, i.e.potentially containing infectious agents capable of causing infection inhumans or animals. Such regulated medical waste may include, but is notlimited to, tissue, cloth, plastic, paper, animal carcasses, bedding andother matter potentially containing infectious agents.

[0004] Recently, Health-care organizations as well as RegulatoryAgencies have been concerned with the adequacy of existing cleaning anddisposal methods. It has been discovered that some potentially harmfulcells, such as prokaryotes, or harmful proteins may survive standardautoclaving procedures. Thus, more effective sterilization techniqueshave been sought for treating solid infectious biomedical waste, i.e.,regulated medical waste.

[0005] In addition, universities and other research facilities likewiseproduce a significant level of such waste. In conducting experiments incell lines, tissues or upon animals, it is common to introduce dyes,toxic chemicals or infectious agents into the test subject. Aftercompletion of the test and analysis, due to the introduction ofinfectious agents or hazardous materials, the remaining tissue or animalcarcass falls under the classification of regulated medical waste. Inaddition, animal waste, animal bedding, handling materials and othermatter exposed to animal body fluids or excretions may also need to betreated as infectious or hazardous waste, thus requiring disposal inaccordance with applicable governmental regulations.

[0006] In addition, it is common for health care organizations today toclean materials, instruments or surface areas exposed to infectiousagents, including zoonotic agents, with disinfectants such asformaldehyde or glutaraldehyde. Spent cleaning solution is consideredhazardous liquid waste and must be disposed of in compliance withgovernment regulations. The cost of disposing of such waste, on aninstitutional basis, can be quite costly. In addition, formaldehyde,glutaraldehyde, phenols and like materials are commonly used forembalming tissues and in fixation of infectious biological materials.Thus, these tissues and the fixative agents must likewise be disposed ofin compliance with government regulations.

[0007] Currently, the two methods commonly used in disposing ofhazardous waste and regulated medical waste are incineration and burial.Presently Federal law imposes strict regulations for incineration ofhazardous waste and infectious biomedical waste. However, incinerationmay be further limited by state and local agencies. For example,incineration of regulated medical waste or other hazardous waste is notavailable at all in some jurisdictions such as the major metropolitanareas of New York City, San Francisco and Chicago. Furthermore, thegeneral process of incineration itself, even when no hazardous materialsor regulated medical wastes are involved, is subject to additionalregulations, such as those requiring a direct license from a state orlocal environmental agency. Additionally, future increases in therequirements for incinerator designs and function under clean airregulations put in doubt the continued availability of incineration as amethod of disposing such wastes.

[0008] Presently, the only real alternative to incineration isautoclaving the solid waste and then burying the waste material in alicensed waste disposal facility. Currently there are a limited numberof such sites in the United States. It is extremely costly to dispose ofinfectious medical waste by this method. Further, one will appreciatethat the cost is exceedingly high for waste that comprises matter which,but for the potential infectious agents, could be disposed of using lesscostly local disposal facilities. Due to the extremely high costassociated with land burial and the limitations on access to licensedland burial sites, the feasibility of land burial as a method ofdisposing of such waste remains an ever growing concern for research andhealth-care facilities.

[0009] The known methods of disposing of regulated medical wastesgenerated by many universities, health-care and research facilitiesfaces an uncertain future under the ever narrowing scope ofenvironmental laws. Furthermore each is extremely costly, putting anunneeded drain on the already strained resources of universities,health-care organizations and research facilities. Thus, a need existsfor methods for disposing of infectious biomedical wastes and otherhazardous materials which is safe, environmentally friendly and lessexpensive than existing disposal means.

SUMMARY OF INVENTION

[0010] The aforesaid needs are satisfied and the limitations of theprior art overcome, in accordance with the principles of the presentinvention, by providing a method for producing safely disposablecompositions from regulated medical waste. This method for treatingregulated medical waste comprises the steps of providing a highly basicsolvent, immersing the regulated medical waste within the highly basicsolvent, and heating. The regulated medical waste contains infectiousagents, which comprise hydrolyzable material (i.e. biological tissues,cells, or cell components containing proteins or lipids capable ofundergoing hydrolysis or saponification in the highly basic solvent).Furthermore, the infectious agents are capable of causing infection inhumans or animals and are selected from the group consisting ofbacteria, organisms, and proteinaceous material.

[0011] To assure degradation of all infectious wastes, includingprokaryotes, the heating step comprises heating the highly basic solventand immersed regulated medical waste to a temperature greater than 130°C. and under an absolute pressure greater than 2.79 atmospheres (gaugepressure>1.79 atm) and for a time sufficient to digest the hydrolyzablematerial. A sterile solution comprising non-toxic biodegradablematerials and containing sterile solid waste free of infectious agentsis produced. Degradation of the regulated medical waste preferablyinvolves treating the waste at a temperature around 135° C. and under anabsolute pressure about 3.1 atmospheres (gauge pressure about 2.1 atm),and more preferably, around 150° C. to 155° C. and about 5 atmospheres(gauge pressure about 4 atmospheres). At a temperature around 180° C.,the corresponding pressure will be about 10 atmospheres (gauge pressureabout 9 atm). Generally, it is preferable not to exceed temperatures ofabout 180° C. Unless indicated otherwise, pressures herein are absolutein atmospheric units, and the corrresponding gauge pressure reading maybe calculated by subtracting 1 atmosphere from the absolute pressure.

[0012] The tissue or other matter potentially containing the infectiousmedical waste is allowed to remain within the highly basic solvent untilthe hydrolyzable matter is fully digested, thereby forming a sterilesolution and sterile solid waste. The aqueous solution and any solidwaste may then be disposed of through standard means, such as a sanitarysewage system and local landfill facilities. However, it will beappreciated that the amount of solid waste to be disposed of issubstantially reduced by the present invention.

[0013] In another aspect, hazardous materials may be removed from thedigest and separately disposed of in an appropriate manner, such as in alandfill designated for such hazardous wastes or in a specially licensedhigh temperature furnace. Paraffin or wax may be added to the regulatedmedical waste prior to or after digestion. Upon heating of thematerials, the paraffin or wax melts and becomes distributed throughoutthe aqueous solution. After the waste has been fully digested and theaqueous solution is allowed to cool, the lipid-like materials separateout from and float to the surface of the aqueous phase where theyresolidify upon cooling to room temperature. Lipid soluble wastematerials may then be removed from the aqueous phase upon separation ofthe lipid phase because they have become incorporated within the lipidphase. Thus, removing the lipid phase from the solution effectively alsoremoves lipid soluble hazardous materials not degraded or otherwiseconsumed in the alkaline treatment.

[0014] Accordingly, it is a principle object of this invention toprovide a method for safely disposing of tissue and other mattercontaining infectious biological waste (i.e., regulated medical waste)and/or other hazardous materials. One advantage of this invention isthat it allows for safe disposal of the regulated medical waste atsignificantly less expense to the research or health-care facilitywithout harming or increasing the risk of harm to the environment. Anadditional advantage of this invention is that the method may beutilized without geographic limitations, satisfying existinggovernmental regulations at the federal, state and local level. Anotheradvantage of this invention is that it preserves the ever shrinking areaavailable in the land burial sites.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 shows a partial cut-away elevated view of an apparatus forpracticing the present invention.

[0016]FIG. 2 shows a view of a screen mesh permeable container.

[0017]FIG. 3 shows an elevated view of a solid permeable container.

[0018]FIG. 4 shows a partial cut-away elevated view of an apparatus forpracticing the present invention utilizing a plurality of tanks.

[0019]FIG. 5 shows a schematic drawing of an apparatus for practicingthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] This invention involves a method for safely treating anddisposing of matter containing infectious medical waste (i.e., regulatedmedical waste) and/or hazardous waste materials and is designed andintended to comply with all federal, state and local laws or regulationsapplicable to disposal of such wastes. In general, as is commonly knownto those of skill in the art regarding various types of waste disposal,and as used herein, regulated medical waste does not contain radioactivematerial, and radioactive material does not contain regulated medicalwaste or infectious agents. In fact, as is commonly known, low levelradioactive biological waste and infectious waste are two very differentand completely separate waste streams regulated by different laws andregulations, as well as by different agencies. Processes intended forthe treatment and disposal of one of these waste streams would not beexpected to be applicable to the other.

[0021] With this in mind, in one aspect the method comprises the stepsof immersing regulated medical waste, as defined above, within a highlybasic solvent. The highly basic solvent is heated to a temperaturegreater than 130° C. under an absolute pressure greater than 2.79atmospheres, preferably at a temperature around 135° C. and a pressureof about 3.1 atmospheres, but more preferably, at a temperature rangingfrom about 150° C. to about 155° C. and under an absolute pressure ofabout 5 atmospheres. Also, it is preferable to limit the temperature ofthe solvent to about 180° C., which corresponds to an absolute pressureof about 10 atmospheres. Furthermore, the reaction should be conductedin a sealed vessel, as described below, to reach the desired pressure.The pH of the highly basic solvent is preferably at least 12 and mayvary up to 14. The aforementioned reaction conditions assure thecomplete degradation of all infectious wastes, including prokaryotes.

[0022] The tissue or other matter containing regulated medical waste,and optionally, hazardous waste material, as described below, is allowedto remain within the highly basic solvent until fully digested, therebyforming a sterile partially neutralized aqueous solution and sterilesolid waste free of infectious agents, such as zoonotic agents or otherhazardous materials. As used herein, “infectious agents” refers tobacteria or organisms or proteinaceous material capable of causinginfection in humans or animals including, but not limited to, zoonoticagents and prokaryotes. “Sterile” and “sterilized” mean being free ofinfectious agents.

[0023] When the researcher is ready to dispose of the regulated medicalwaste, the waste is completely immersed in a highly basic solvent.Preferably, this solvent should have a pH of 12 to 14, and it may becomprised of a mixture of water and an alkali metal hydroxide,alkaline-earth metal hydroxide, or alkaline-earth metal oxide, such ascalcium oxide. An aqueous solution of NaOH and/or KOH is preferred. Anexample of such a suitable highly basic solvent may consist of a 0.1molar to 2.5 molar solution of NaOH in water, or approximately 0.4%-10%sodium hydroxide (by weight) in water. It has been discovered thatgelation of the digest upon flushing with cold water may be avoided byusing a highly basic solvent of 1.5 M NaOH or 1.0 molar KOH, or more.Calcium oxide is typically used at a pH of 12 in cases where there is nofat, for example, when the waste is meat, bone meal, blood, etc.

[0024] The waste should be immersed in enough highly basic solvent suchthat all biological tissues, cells, and cell components are completelydigested; namely, hydrolyzing tissue proteins by breaking many of thepeptide bonds and saponifying cell and tissue lipids. The terms“digested”, “degraded”, “neutralized”, “treated” and forms thereof areinterchangeable, as used herein. Also, as used herein, “hydrolyzablematerial” refers to biological tissues, cells or cell components thatcontain proteins or lipids capable of undergoing hydrolysis orsaponification in the highly basic solvent. To ensure complete digestionof the hydrolyzable material, excess base is preferably used. One ratioassuring excess base to carry out the digestion of the waste tocompletion is a 1:10 ratio of sodium hydroxide to wet tissue weight. Afurther expression of this ratio is 40 kilograms NaOH in 500 liters H₂Oadded to 500 kilograms tissue by weight. These ratios are given only asinstruction as how to conduct the method stated herein and not to limitthe nature of the invention; one using the method described herein mayfind ratios more economical and exact as the invention is practiced. Itwill be appreciated that lower ratios of alkali to waste may be used asthe degree of non-organic matter, such as glass and plastic, increases.

[0025] If the reaction between the regulated medical waste and highlybasic solvent were allowed to proceed at its natural rate, it may takean impractical amount of time. Conducting the reaction in a sealedvessel under increased pressure and temperature reduces the reactiontime needed to completely digest the tissue, cells and cell components.Pressures greater than 2.79 atmospheres (and temperatures greater than130° C.) are used in this regard, with pressures preferably up to aboutten atmospheres (temperatures up to about 180° C.). Furthermore,detergents at a concentration of up to 1% by weight, examples beingsodium lauryl sulfate or deoxycholate, may be added to the highly basicsolvent. It should also be noted that, if no lipid soluble hazardouswastes are to be recovered, the addition of detergents also has theadvantage of dispersing non-saponifiable lipids, and aiding in thesterilization of biological materials.

[0026] In addition, shredding the solid waste prior to immersion withinthe highly basic solvent reduces the reaction time by making moresurface area accessible to the highly basic solvent. Still anothermethod capable of reducing the reaction time is provided by supplying anexcess of fresh highly basic solvent continuously onto the surface ofthe solid waste. This may be accomplished by agitating, circulating orstirring the solvent.

[0027] The reaction rate will ultimately depend on specific variablessuch as: the temperature of the solvent, pressure in the reactionvessels, nature of the waste and ratio of hydrolyzable material to thevolume of the highly basic solvent. As the reaction rate will vary, thetime that the waste must remain immersed in the highly basic solventwill also vary. However, regardless of the reaction rate, the wasteshould remain immersed within the highly basic solvent until thehydrolyzable matter is fully digested. Leaving the waste within theheated highly basic solution until complete digestion is achievedassures production of a sterile solution. Using excess base at atemperature greater than 130° C. and an absolute pressure greater than2.79 atm, digestion will, in almost all instances, be complete after 8-9hours. More preferably, however, the temperature should range from about135° C. to 180° C. At a temperature ranging from about 150° C. to about155° C. and at a pressure of about 5 atmospheres (65 psig), digestionmay be complete in as little as 3 hours.

[0028] Once the animal tissue has been completely digested, neutralized,and treated, two types of solid debris often remain. As used herein, theterm “sterile solid waste” includes the following two types of soliddebris. The first type of debris consists of metal, rubber or plastic,such as surgical clips, sutures, glass, and other pieces of plastic orpaper. Solid items such as these do not incorporate infectious medicalwaste and are completely sterilized after treatment. Thus, the treatedsolids may safely be disposed as ordinary sterile solid waste afterbeing isolated from the solution and washed. The second type of soliddebris remaining undissolved includes inorganic portions of the animal'sskeletal structure. After treatment, all organic components of theskeletal structure are digested, leaving sterile calcium phosphate. Theskeletal remains, when removed from the highly basic solvent and washed,are extremely friable and may be easily crushed. In fact, the skeletalremains are so friable that they may be crushed to form a disposablepowder by such relatively simple means as manual application ofpressure.

[0029] After the waste has been fully digested within the highly basicsolvent and the solid debris removed, the remaining “sterile solution”will comprise a sterile mixture of alkali metal salts (or alkaline-earthmetal salts) of amino acids, sugar acids, nucleotides, small peptides,fatty acids from lipids, phosphates from lipids and nucleic acidbreakdown, soluble calcium salts, pigments, sugars, sugar alcohols,hydrocarbons and inorganic acids derived from the electrolytes normallyfound within tissue fluids. However, due to the heated alkalinetreatment, infectious agents, including zoonotic agents and prokaryotes,are broken down into low molecular weight residues. Thus, it is entirelysafe to dispose of the treated solution and solids using disposal meanssuch as septic tanks, sewage systems, local landfills and other disposalmeans appropriate for the disposal of these simple non-hazardousmaterials.

[0030] Because the sterile solution at the end of the reaction processcontains only non-toxic biodegradable materials, dilution of thesolution may not be required for disposal. However, reducing thealkalinity the solution may be accomplished by diluting the solution,such as by adding excess water to the reaction vessel before it isdischarged or as it is being discharged. With the majority ofapplications the resulting solution is well within the level ofalkalinity that is safely disposable as sanitary sewage. Dilution mayalso be accomplished by one skilled in the art by calculation of thedilution of the specific unit of waste volume by the entire waste volumeof the institution or manufacturing plant.

[0031] As indicated above, it is common to clean instruments and surfaceareas exposed to infectious agents with formaldehyde, glutaraldehyde andlike agents. In addition, formaldehyde, glutaraldehyde, phenols and likematerials are commonly used as fixating agents for biological tissues.Spent cleaning solution and fixatives are considered hazardous wastematerials which must be disposed of in accord with applicablegovernmental regulations. As used herein, the term “hazardous wastesolution” refers to spent cleaning solution or fixative and comprisesinfectious agents (containing hydrolyzable material) in solution with amaterial selected from the group consisting of formaldehyde,glutaraldehyde, phenols, mixtures of formaldehyde and glutaraldehyde,mixtures of formaldehyde and phenols, and mixtures of glutaraldehyde andphenols.

[0032] It has been discovered that spent cleaning solutions offormaldehyde, glutaraldehyde, phenols, and various combinations thereof,may be safely disposed of together with the digestion of regulatedmedical wastes (i.e.,containing infectious agents). For example, up to30 gallons of formaldehyde or glutaraldehyde, typically a 2-4% solutionby weight, may be degraded in conjunction with 250 lbs. of tissue.Hazardous materials containing, for example, formaldehyde,glutaraldehyde, phenols, or mixtures thereof, and similar materialsreact in the above alkaline treatment to form harmless non-toxicmaterials. For example, when formaldehyde and phenol are in solutionunder the alkaline conditions a harmless inert plastic like material isformed. Also, the aldehydes by themselves react irreversibly with thetissue amino groups to form harmless products. Thus, the term “sterilesolid waste” also includes the aforementioned plastic like material andharmless products.

[0033] However, not all hazardous materials will break down into inertby-products under the temperature and conditions described above. Thus,when the regulated medical waste material incorporates hazardousmaterials capable of withstanding the above conditions, additional stepsmust be undertaken to ensure degradation or extraction of the hazardousmaterials within the resulting solution. Lipid soluble hazardousmaterials, such as halogenated aliphatic and aromatic hydrocarbons,PCBs, chlorinated insecticides, many dyes and materials of likesolubility may be extracted from the aqueous digest based on theirsolubility in lipids. Paraffin or wax, preferably in solid form, may beadded to the waste material to be digested. Upon heating, the addedmaterials melt and, with the aid of the soaps formed during alkalinesaponification of fatty tissue, the materials become finely dispersedthroughout the digest. After digestion is completed, the mixture isallowed to cool to room temperature (about 20° C. to about 25° C.),preferably without stirring. The lipid phase separates from the aqueousphase upon cooling and due to the solubility characteristics of thehazardous material, the lipid phase incorporates the lipid-solublehazardous waste. The solid lipid phase floating on the top of theaqueous phase may then be easily removed from the digest, such as bystraining. Thus, this method avoids the difficult and costly proceduresassociated with most liquid-liquid extractions. The resolidified solidlipid material, such as a paraffin cake, may then be disposed ofaccordingly. For example, where the solid lipid contains toxic or highlyregulated materials, such as PCBs, the solid lipid extract may bedisposed in the appropriate hazardous waste facility. This extractionprocess may be repeated, if necessary, for lipid-soluble compounds withpartial solubility in the aqueous phase to allow for quantitativeextraction of such compounds.

[0034] In this regard it is important to note that the volume of thehazardous material, and hence the cost in properly disposing of thesame, has been considerably reduced since the large constituent ofharmless biodegradable organic mater, such as peptides, sugars and aminoacids have been separated from the toxic substance. Suitable paraffinsand waxes include, but are not limited to ordinary household paraffins,carnauba wax, bees wax, mixtures of alkanes, and mixtures ofhydrocarbons, long chain fatty acids, esters and alcohols that aresolids at room temperature. In the event the hazardous material isinsoluble in lipids, other known liquid-liquid extraction methods may beemployed, the specific application of which will vary with regard to theparticular hazardous material.

[0035] Disposal of the regulated medical waste should be prompt becausethe organic material begins to decompose immediately under roomtemperatures. Thus, the regulated waste must be dealt with soon after itis produced in order to avoid the creation of noxious odors and otherhealth hazards. However, freezing of the regulated medical wasteeffectively prevents decomposition and the creation of noxious odors andhealth hazards. Thus, when it is not economical or practically feasibleto dispose of the waste on a daily basis, the regulated medical wastemay be frozen and stored in that condition until an appropriate time oramount of waste for disposal is acquired. Temporary storage of the wasteby freezing may be accomplished by any refrigeration means capable ofmaintaining a temperature of 0 Celsius or below and capable of storingthe amount of waste desired.

[0036] An apparatus for producing a safely disposable solution fromregulated medical waste can be seen in reference to FIGS. 1-5, such anapparatus comprises the following elements: a sealable tank 10 with ahighly basic solvent 12 therein, a permeable container 22 for storingregulated medical waste, a water supply means 28, a filtering means 20,a pressurizing and venting means 15 and a disposal means 32.

[0037] A preferred apparatus comprises a singular tank or vessel capableof containing a solution. The tank must be made of a material that iscapable of withstanding the pH levels, temperatures and pressuresutilized in this process, an example being stainless steel.

[0038] The reaction between the highly basic solvent 12 and theregulated medical waste, such as the tissue, cloth, paper or othermatter, takes place within a tank 10. However, it is preferable for thereaction to occur within a closed reaction vessel in order to preventCO₂ from the atmosphere from entering the reaction path. Thus, the tank10 preferably has a sealing means 14 capable of withstanding thechemicals, temperatures and pressures utilized in this process, anexample being stainless steel. Because absolute pressures greater than2.79 atmospheres are utilized, the sealing means 14 must be pressure andair tight. This may be accomplished through the use of an alkaliresistant gasket and a cover sealed to the tank with clamps 16. Apressurizing means 15 may be fitted to sealed tank 10 in order toincrease the pressure therein. Furthermore, in an alternative embodimentthe sealing means 14 may also contain a pressure gauge to monitor thereaction vessel, adjustable safety valves, and a sampling port 17 formeasurement of the pH of the reaction mixture.

[0039] As discussed above, the process requires that the highly basicsolution 12 be heated in order to assure degradation of all infectiousagents and proper sterilization of the solid matter. Therefore, aheating means 18 is necessary to heat the highly basic solvent 12. Anyheating means 18 commonly known and used today for heating solutionscould be utilized in this process. One example of such a heating means18 is a stainless steel heating jacket, in which heated water or steamcirculates between the walls of a double walled tank, thereby heatingthe solution within the tank. Alternatively, the tank 10 may be fittedwith an electric heating mantle, placed upon a hot pad, or fitted withan internal heating coil.

[0040] As discussed above, after the hydrolyzable waste has been fullydigested, there often remains undigested solid debris, i.e. skeletalremains, glass or plastic. Thus, the preferred embodiment contains afiltering means 20, as shown in FIG. 1., for removing the solid debrisbefore or during disposal of the sterile solution. An example of asuitable filter would be a 40 mesh/25.4 mm stainless steel screen. Thefiltering means 20 may be placed in combination with the removal means30 such that the sterile solution is filtered as it is removed from thetank 10.

[0041] The apparatus may also have a permeable container 22 capable ofholding the waste. The permeable container 22 may be utilized to immersethe waste within the highly basic solvent 12. This container may alsoact as the filtering means and/or a means for removing the solid sterileundigested debris. When the hydrolyzable matter is fully digested, thepermeable container 22 may be removed, thereby removing the undigestedsolid debris remaining within the permeable container 22. The containershould be made of a material capable of withstanding the pH levels,chemicals and temperatures involved in this process. In addition, thecontainer should be permeable to liquids, small peptides and aminoacids. An example of such a container can be seen in reference to FIG. 2and FIG. 3. A container having 3.2 to 6.4 mm stainless steel screen meshbasket may suffice in practicing the method disclosed herein, such ascan be seen in FIG. 2. When a large amount of waste is to be moved orheld, the screen mesh basket should be reinforced with stainless steelbands. Alternatively, as seen in FIG. 3, the container may comprise of asolid stainless steel container with 3.2 or 6.4 mm holes drilledtherein. These baskets may be shaped and sized to be removably fittedwithin of the above mentioned tank 10, with sufficient clearance toallow liquid to circulate over all surfaces of its contents. It is alsopossible that these containers could be sized such that they fit withinthe refrigeration means 40, as shown in FIG. 4, thereby reducing thework and components necessary to complete this process.

[0042] Because the natural reaction time is very slow, the preferredinvention may also contain an agitating means 24 to help speed up thereaction rate by keeping the solvent or the substrate in motion whilethe reaction is taking place. A means for agitating or simply moving thesolid undigested waste within the highly basic solvent 12 may accomplishits task by simply moving the permeable container 22 holding the animalremains. In addition, it is also possible to accomplish the same resultby circulating the highly basic solvent 12. This may be accomplished bya wide variety of means well known in the art today, examples beingmechanical stirrers or pumping means. However, any pump connected to thetank 10 via piping and valves must be capable of withstanding thetemperatures, chemicals and pressure involved.

[0043] An exhaustion or ventilation means 26 such as a ventilated hoodmay be placed over the tank 10 and be positively ventilated in order toremove any excess carbon dioxide or noxious fumes produced by performingthe method disclosed herein.

[0044] Depending on the size of the tanks 10 and the amount ofhydrolyzable waste being digested, it may be possible to dilute theresulting sterile solution, directly within the tank 10 before drainingsaid tank 10. However, not all tanks will be large enough to dilute themixture created by the reaction. In such a case, dilution may occursimultaneously with draining of the tank 10. In either case, it isnecessary to have a water supply means 28, preferably with a stop valve29. The appropriate amount of water may be added as the solution drainsor is pumped from the tank 10. This may be accomplished with any meansfor adding water, examples being any faucet, hose or lead connected to awater supply capable of delivering the rates necessary.

[0045] Finally, an apparatus for practicing the present invention maycontain a means for emptying the contents 30 of the tank 10. One maysimply use a drainage port and let gravity drain the solution from thetanks. Such a port would preferably be fitted with a removable screenfilter 20 to retain small non-hydrolyzable materials that may haveescaped from the basket during the digestion process. Alternatively,pumps may be used to drain the tanks of their contents. However, anypump utilized in this apparatus should be made of stainless steel withall seals and liners made of a material capable of withstanding strongalkaline action; an example being TEFLON®. Materials such as glass,ceramics, rubber, and most synthetics should not be used due to theirvulnerability to alkaline actions. The piping and valves used in thecirculation of the solvent may be linked to or comprise the same pipingand valves utilized in the draining and flushing of the tank. Inaddition, if a pump is utilized to circulate the highly basic solvent 12this same pump may be utilized to drain the reaction mixture.

[0046] Preferred safety controls on any drainage system would includemeasurements of pH by port sampling or continuous flow analysis withinput of both sets of data going to a manually or electronicallycontrolled valving system. Specifically, manual or automated systemsmust receive information on the final pH of the solvent at thecompletion of the digestion process before dilution can be calculatedand implemented in order to initiate discharge of the vessel.

[0047] An alternative embodiment of an apparatus for practicing thepresent invention is shown in FIG. 4, comprising a plurality of tanks, ahighly basic solution 12 within the first tank 34, a less basic solution37 in the second tank 36, a neutral solution 39 in the third tank 38,and means for removing the solutions 30 therein. The first tank 34 mayhave additional modifications shown in FIG. 1, unlike the additionaltanks, such as a heating means 18, a sealing means 14, an agitatingmeans 24, and a pressurizing means 17. Since these modifications areonly necessary for the tank in which the reaction actually takes place,any additional tanks would not require these modifications. Furthercomprising the alternative apparatus in FIG. 4 are a refrigeration means40 for storage of the waste, a means for moving the permeable container42, a ventilation means 26, a water supply means 28 and a disposal means32.

[0048] As can be seen from FIG. 4, it is possible for the apparatus toutilize a plurality of tanks. The tanks may be located in proximity toone another such as in a linear or circular series. When a single tankis used, this tank will contain the highly basic solvent 12. However,when a plurality of tanks is used, the first tank 34 in the series maycontain a highly basic solvent 12 and the second tank 36 and subsequenttanks containing a less basic solution. Preferably, the second tank 36contains a solution 37 having a pH of approximately 10. The solution ofthe second tank 36 may be comprised of one percent sodium hypochlorite;i.e., a 1:5 dilution of household chlorine bleach and water. The thirdtank 38 in the series may contain a solution 39 having a pH ofapproximately 7, such as water. The second and third tanks may beutilized to rinse off the highly basic solvent 12 that remains upon thepermeable container 22 and the solid non-hydrolyzable debris. This maybe accomplished by moving the permeable container 22 and/or solid debrissequentially through the tanks. Use of all three tanks is optional asuse of either 1, 2, 3 or more tanks is possible. When only two tanks areutilized, it is preferable for the second tank to contain a solutionhaving a pH of approximately 7, such as water.

[0049] It may also be necessary to provide a means for moving thecontainer 42 housing the waste therein. The means necessary to completethis function is highly dependent upon the amount of waste a intended tobe disposed. If it is to be done in small amounts and, therefore smallweights are involved, a less sophisticated or complex means could beused. Possible means range from simple winch and pulley systems to moremechanized apparatus such as forklifts, hydraulic apparatus, ormechanized winches. It may be advantageous that the moving means 42 besized such that it can move the containers from tank 34 to tank 36 witha hood 26 remaining in place over the tanks.

[0050] A further component of the apparatus may include a freezer 40. Asindicated above, it may be desirous to store the tissue or other mattercontaining infectious waste for a period of time before disposing of theanimal tissue a freezer when disposal is not conducted on a daily basis.

[0051] As can be seen in reference to FIG. 5, other embodiments capableof manual or automated operation may be designed without departing fromthe scope of the present invention. This particular embodiment disclosesa sealable tank 10 having a top lid 44, a water inlet port 46, an airvent 48 and pressure gauge 50. A steam jacket 52 surrounds the length ofthe tank 10 and has separate condensate outlet 54 and steam inlet 56on-off valves. Condensate outlet 54 may also be used as a cooling waterinlet to circulate cooling water into jacket 52, and steam inlet 56 maybe used to exit the cooling water from the jacket. A single pump 58 maybe used and is connected to the various drainage and sampling ports viaa system of connecting pipes and valves, such as the pump to vesselshut-off valve 60, the sampling valve 62, the pump to drainage shutoffvalve 64 and the lower pipe drainage and alkali inlet valve 68. Thebottom of tank 10 is also fitted with a temperature sensor 72. All ofwhich may be run manually or by an automating means, such as amicroprocessor connected to the various sensors, pumps and valves.

[0052] Although the invention has been described in the terms of thepreferred embodiments, it is apparent to those skilled in the art thatvarious modifications, substitutions, equivalents and other changes maybe utilized without departing from the spirit of the invention.

We claim:
 1. A method for treating regulated medical waste comprisingthe steps of: (a) providing a highly basic solvent; (b) immersing saidregulated medical waste into said highly basic solvent, wherein saidregulated medical waste contains infectious agents comprisinghydrolyzable material, wherein said infectious agents are capable ofcausing infection in humans or animals and are selected from the groupconsisting of bacteria, organisms, and proteinaceous material; and (c)heating said highly basic solvent and said immersed regulated medicalwaste to a temperature greater than 130° C. and under a pressure greaterthan 2.79 atmospheres and for a time sufficient to digest saidhydrolyzable material, whereby a sterile solution comprising non-toxicbiodegradable materials and containing sterile solid waste free of saidinfectious agents is produced.
 2. The method of claim 1 , wherein saidhighly basic solvent has a pH of at least 12 up to about
 14. 3. Themethod of claim 1 , wherein said highly basic solvent comprises amixture of water and an alkali metal hydroxide, alkaline-earth-metalhydroxide, or alkaline-earth metal oxide.
 5. The method of claim 2 ,wherein said temperature maximum is about 180° C.
 6. The method of claim2 , wherein said temperature ranges from about 135° C. to about 180° C.,and said pressure ranges from about 3.1 atmospheres to about 10atmospheres, respectively.
 7. The method of claim 6 , wherein saidtemperature ranges from about 150° C. to about 155° C., and saidpressure is about 5 atmospheres.
 8. The method of claim 1 , wherein saidhighly basic solvent also includes a detergent at a concentration of upto about 1% by weight.
 9. The method of claim 1 further comprising instep (b) adding a hazardous waste solution into said highly basicsolvent, wherein said hazardous waste solution also contains saidinfectious agents comprising hydrolyzable material.
 10. The method ofclaim 9 , wherein said hazardous waste solution comprises infectiousagents in solution with a material selected from the group consisting offormaldehyde, glutaraldehyde, phenols, mixtures of formaldehyde andglutaraldehyde, mixtures of formaldehyde and phenols, and mixtures ofglutaraldehyde and phenols.
 11. The method of claim 1 , wherein saidregulated medical waste further contains lipid soluble hazardousmaterial, said method further comprising between steps (b) and (c) thestep of adding a paraffin or wax to said highly basic solvent containingsaid regulated medical waste, wherein upon heating in step (c) saidlipid soluble hazardous material and said paraffin or wax are dispersedthroughout said sterile solution.
 12. The method of claim 11 furthercomprising after step (c) a cooling step, wherein upon cooling to roomtemperature, said lipid soluble hazardous material and said paraffin orwax separate from said sterile solution to form a solid lipid phase atopsaid sterile solution.
 13. The method of claim 12 further comprisingremoving said solid lipid phase.
 14. The method of claim 1 , whereinsaid regulated medical waste further contains lipid soluble hazardousmaterial, said method further comprising in step (c) adding a paraffinor wax to said highly basic solvent containing said regulated medicalwaste, wherein upon heating in step (c), said lipid soluble hazardousmaterial and said paraffin or wax are dispersed throughout said sterilesolution.
 15. The method of claim 14 further comprising after step (c) acooling step, wherein upon cooling to room temperature, said lipidsoluble hazardous material and said paraffin or wax separate fromsterile solution to form a solid lipid phase atop said sterile solution.16. The method of claim 15 further comprising removing said solid lipidphase.
 17. The method of claim 1 further comprising agitating,circulating, or stirring the highly basic solvent in step (c).
 18. Themethod of claim 1 further comprising reducing the alkalinity of saidsterile solution by dilution with water.
 19. The method of claim 1further comprising disposing of said sterile solution and said sterilesolid waste.
 20. The method of claim 1 further comprising the step ofremoving said sterile solid waste from said sterile solution.
 21. Amethod for removing infectious agents from a hazardous waste solutioncomprising the steps of: (a) providing a highly basic solvent having apH of at least 12 up to about 14; (b) contacting said hazardous wastesolution containing said infectious agents and said highly basicsolvent, wherein said infectious agents comprise hydrolyzable material,and wherein said infectious agents are capable of causing infection inhumans or animals and are selected from the group consisting ofbacteria, organisms, and proteinaceous material; and (c) heating saidhighly basic solvent and said hazardous waste solution to a temperaturegreater than 130° C. and at a pressure greater than 2.79 atmospheres andfor a time sufficient to digest said hydrolyzable material, whereby asterile solution comprising non-toxic biodegradable materials andcontaining sterile solid waste free of said infectious agents isproduced.
 22. The method of claim 21 , wherein said hazardous wastesolution comprises infectious agents in solution with a materialselected from the group consisting of formaldehyde, glutaraldehyde,phenols, mixtures of formaldehyde and glutaraldehyde, mixtures offormaldehyde and phenols, and mixtures of glutaraldehyde and phenols.23. A method for producing a sterile solution from a hazardous wastesolution comprising the steps of: (a) providing a highly basic solventhaving a pH of at least 12 up to about 14; (b) contacting said hazardouswaste solution and said highly basic solvent, wherein said hazardouswaste solution comprises hydrolyzable material selected from the groupconsisting of biological tissues, cells, or cell components, in solutionwith a material selected from the group consisting of formaldehyde,glutaraldehyde, phenols, mixtures of formaldehyde and glutaraldehyde,mixtures of formaldehyde and phenols, and mixtures of glutaraldehyde andphenols; and (c) heating said highly basic solvent and said hazardouswaste solution to a temperature greater than 130° C. and at a pressuregreater than 2.79 atmospheres and for a time sufficient to digest saidhydrolyzable material, whereby a sterile solution comprising non-toxicbiodegradable materials and containing sterile solid waste is produced.